Method of preparing plywood planking for compound bending



INVENTOR.

O. P. BURCH METHOD OF' PREPARING PLYWOOD PLANKING FOR COMPOUND BENDING Filled Nov. 12, 1958 3 She'ets-Sheet 1 OBEN P. Bue# www@ TTOR/YEYJ April 18, 1961 o. P. BURCH 2,980,153

METHOD OF' PREPARING PLYWOOD PLANKING FOR COMPOUND BENDING Filed Nov. l2, 1958 3 Sheets-Sheet 2 INVENTOR. OKEN F. BuRcH O. P. BU RCH April 18, 1961 METHOD OF' PREPARING PLYWOOD PLANKING FOR COMPOUND BENDING Filed Nov. l2, 1958 5 Sheets-Sheet 5 mm mE U w@ p' m :United States This invention relates to boats and to methods of building boats. More particularly it has reference to improvements in methods of building the hulls of what are generally referred to as pleasure boats, but not necessarily confined thereto, from plywood.

Row boats and pleasure boats, as designed for propul-Y sion by inboard as well as outboard motors, have heretofore been built with hulls formed principally from plywood. However, it has not been possible to giveV to plywood formed hulls the'more yattractive lines, curves o-r shapes that are possible when made of plastic or fiber glass; this being due in most part to the fact that plywood panels do not lend themselves to compound bending such as, for example, that bending that is desired especially in the shaping of the prow forming portions ofthe hull. T It. has been the principal object of this invention to' provide a method Vof preparing plywood hull forming panels, or what will hereinafter be designated as planksj` that permits them to be readily given the compound bends, curves or shapes that are so desired in boat buildatout() Fig. 4 is a cross-sectional detail of a portion of a boat hull showing the keel and chine joints. Fig. 5 is a perspective view illustrating a means for and the manner of clamping the prepared side and bottom planks of a boat hull-to a mold for their pre-shaping treatment.

Fig. 6 is a perspective view illustrating a means for the steam or hot water treatment of the prepared planks after they have been clamped to the mold.

Fig. 7 illustrates the application of the pre-shaped plywood planks to the frame structure of a boat.

Fig. 8Yis'a front end view of a finished boat, illustrating the'transverse curvature given to side and bottom forming planks. l Fig. 9 illustrates'the application of prepared and preshaped plywood plank'to a boat having a planked under ing as a means of enhancing the design and bettering the frame structure.

Fig. 10 is a cross-sectional view of the boat of Fig. 9. Fig. 11 (Sheet 2) is an enlarged cross-sectional view of a plank, showing their slitsfor saw kerfs as filled and sealed with a selected plastic.

It-is indicated particularly. in Fig. 7, that the boat f is formed from paired, opposite side planks, of the general character ofthat shown in Fig. l, and paired bottom planks corrrsponding to that of Fig. 2. These planks after being prepared and molded to the desired shapes,

are applied to` thel boat frame, as indicated in Fig. 7. In the.. building of larger boats, it may require the use of two or more planks for each side of the hull and for each of theV paired bottom sections. However, the present methodapplies to all hull forming parts made of plywood regardless of size or design of the boat.

For the present the invention will be considered as applied to the making of a hull for a small sized boat according to the showing in Fig. 7, Where single plywood planks extend lto its full length. For this boat, I have provided paired, opposite side planks 10-10 and paired in the relationship .of the slits to each other and to their'angular direction through the planks and to the gunwhale or chine line of the boat in order to best Suit-the character and degree of the bend tobe made. y .,Sti1l furtherpobjects and'. advantages of` the inven-l tionresideginthe use ofv aplastic filler in .the kerfs .or

slits asformed through 'theplanksto seal them and to restore the original strength to the planks after being shaped ,and before or after .they are secured to the frame structure. of Vthe boat. u g .I f In. accomplishing the above mentioned and other ob.-` jectsl of the invention, I .have provided the improved de: tails of constructiomthe presentpreferred formsof which are illustrated,,n`theaccompanying drawings, wherein: Fig. l is afiat view of Ya plywood side plank as formed invention t0 adporihe. desired Compound bending.

tobest suitv itspresentnse.;

invention topermit its being given .a compound bend.

" fig. 3` isf an enlarged 'crosssectionalview throu'ghfa'slit...

the plankej Loodbottomfplank VVas form'edfwithslits according to the teachings of the present..

bottom planks 1111,which are applied over the usual frame structure such as that ,designated generally in Fig. 7,

, by reference character 12.

A with slits inv accordance with theteaching of the present bend The side forming planks are ,cutA to a predetermined v l `pattern or form such as tha'tl'shown in Fig. 1 wherein it y Tis .indicated that the plank 10 is made from a single three ply panel wherein'theg'raiin of the core materialgdesigvnated by' character'a, is directed transverselyof the plank and that the grain of the inside and outside plys, b and c,

is directed lengthwise of the plank. vT he gunwhale edge g of the plank is here shown to be upwardly curved and the Vchine edge d is hereshown to beV substantially straight from endA to endf'flhefprow edge p is shown here tobe; forwardly and upwardly inclined fromthe straightA lower edge and the sterr'iedge s is substantially at a right langle l -to ther chine edge d. V'IjIowever,'theV particular pattern of each plank would be predetermined so that when ultimately. shaped lto the moldand joined, a boat :hull of the-- desiredv form would be produced` therefrom.:

A. A s wasl previously explained, ,the'principal object of V this",im/enti'on residesin the preparing of the planksfrom L' plywoodpanels andthe specific manner of slitting the planks/toi, permit -theinlto b e given the desired compo-undv y K 'l h'as;hasfbeenfindicated by the showing ofthe 1 frontfendofthe boat, in Fi'giSwhere it isobserved. that y .Y

, that has width. These kerfs as formed in the planks, are

substantially parallel, and their spacing is in n accordance with the extent of compound curvature required. For example, if the compound vbending in any area is to be rather severe, then the spacing of kerfs in that area is quite close. This would apply in the present instance to the prow forming portions of parts -10. As the transverse curvature is decreased, then the 'spacing of the kerfs can be increased accordingly. In the ordinary type of pleasure boats, the spacing of the kerfs in the more sharply curved portion of the prow is about 2 inches, and this gradually is increased as the degree .of curvature is decreased.

It is of importance in the` forming of the saw kerfs in the plywood panels that they terminate at their opposite ends short of the longitudinaledges of the planks. This distance of termination from the plank edges may be from three to four inches. It has been shown in Figs. l and 2 that the termination of the kerfs provides uncut longitudinal opposite edge portions x and y extending the full length of the slit containing areas.

It is also a feature of this invention that the saw kerfs are substantially parallel and also are formed at an angle relative to the longitudinal direction of the plank, as shown in Figs. l and 2, and also are cut at an angle through the pieces, as has been illustrated in Fig. 3.

For most construction, the kerfs extend approximately at an angle of 45 relative to the longitudinal line of the plank, and at an angle of from 45 to' 20 to the face of the plank.

Assuming that the iiat planks 10-10 and 11-11 have been cut from plywood panels to the desired pattern and that the kerfs have been formed therein in the manner heretofore described and as herein illustrated, they are then placed for preforming in position on the corresponding surfaces of a mold of the desired shape such as that designated by numeral 22 in Fig. 5, and are then pressed into conformity therewith. This step is herein referred to as the preforming step or operation, and it is com pleted without subjecting the planks to steam or water treatment. For this pre-forming operation, suitable clamps are employed, such as for example, the clamp Screws 23 shown to be mounted in a frame structure 24 that encloses and mounts the moldV 22. Clamping pressure is applied at ail areas necessary to cause the planks v to conform to the shape of the mold, as indicated in Fig. 5. v

After the planks have been thus brought by the clamping pressure to form and while so held, firmly and securely, Ythey are subjected to a plasticizing treatment that is effected by blowing wet steam or hot water over the outer surfaces of the planks. VThis treatment 'which may be carried out within an enclosure, is continued until the fibers and lignin ot' the wood have become plastic or moldable. Under this treatment the planksrwill lose their natural resiliency` and willV yield into close ,conformityy to the surfaces of the mold. f g

j Various ways and means might beemployed for this treatment, however, in Fig. 6, l have shown theplasticizing apparatus to comprise a plurality of header pipesv 2S from which steam or hot water can be discharged at the pieces of use; the headers being applied about the clamping frame and connected with a supply pipeline 26.

' lively, in accordance with the increase' and decrease of yWhen the plasticizing-treatment hasbeen completed, I

tolcooling and` drying. ...This may be c'aried out bythe the planks, while still held bythe clamps, are subjected blowing of warmed air against the panels through the same piping system employed for the plasticizing treatment.

After the period of cooling, continued until the wood bers have set in the planks as preformed on the mold, the clamps are removed and the plastic filler applied, as in the case of Kit boats, or they are taken from the form and ultimately applied to and secured in the usual way to the frame vstructure 12 provided for the boat. It has been found practical to overlay the abutted edges of the bottom forming planks 11-11 with inside and outside keel strips as shown at 30 and 31 in Fig. 4, and to join the lower edges ofthe sidewall planks 10--10 with the outer edges of the bottom planks, with chine strips as at 32. t is to be understood, however, that any suitable means for and method may be employed for the joining of planks to the frame.

it is further to be explained that the planksso formed might likewise be formed for and applied to `what are designated as double planked boats such as that .illustrated in Figs. 9 and 10, wherein the under planking is designated by numeral 40. The method of preparing the planks iti-1d and 11-11 for double planked boats is not necessarily the plasticizing treatment. The method of securing the outer planking would be in accordance with present day practice.

The final finishing of the boat hull after the sidewall and bottom planks have been secured to the frame is to ll the kerfs with a suitable plasticthat can be applied thereto in liquid or semi-liquid form and which will set as a hard, waterproof bonding and sealing agent. This not only fills the kerfs but, upon setting, restores the original strength of the material. At present, I employ Flex-Bond Mastic. This particular plastic material, after being applied to `the kerfs and over `the surfaces of the planks, can be sanded smooth and Vgiven a high polish by buing.

What I claim as new is:

1. A method of preparing plywood panels for'compound bending, the method comprising forming those areas of the panels that are to be subjected to compound bending with a plurality of substantially parallel saw kerfs cut completely through the thickness of the panel and directed angular'ly across the panels with respect to their lengthwise direction, and said kerfs being directed angularly with respect to the surfaces thereof and terminating at their opposite ends short of the longitudinal edges of the panels thus leaving the panels with uncut opposite edge portions of normal strength and rigidity.

2. The method recitied in claim l wherein the kerfs are cut through the panels approximately at an angle of 45 with respect to their surfaces and at approximately 45 relative to their longitudinal direction.

3. The method recited in claim lkwherein the spacing of the saw kerfs is decreased and increased, respecthe sharpness of the compound bend that yis to be made. 4. In the fabrication of a boat hull from plywood panels; the method` of preparingthe panels for compound bending comprising forming those areaswhich are to be subjected to compound bendingV with a succession of substantially parallel saw kerfs cut completely through and directed angularly across the panels with respect to their longitudinal edges and terminating within said edges thus leaving uncut opposite edgeV portions of normal strength and rigidity, said cuts being-at less than a angle to the surface'of'the panels', thenv clamping saidpanels to a boat `mold tofbendA the panels tothedesired form and subjecting panels Vwhilegso clamped, to

steam heat "suflicient to soften the fibers and. lignin of the panels and eliminate the resiliency of the material, then subjectingthe panelsto drying thus Vto cause the panels to set to the shapeof the mold.

`5. The method recited in claimY 4 including also the l ,1. A. f, I, ar

filling of the saw kerfs as cut through the panels, While clamped to the mold, with a Water proof, hand setting plastic glue, Iand allowing the glue to set and harden and thereafter releasing the clamping force.

6. The method recited in claim wherein the spacing of the saw kerfs is decreased or increased, respectively, in accordance with the increase or decrease in the sharpness of the bends to be made therein, and said saw kerfs are directed across the panels approximately at a 45 angle to their longitudinal edges and are `cut through the panels at approximately a 45 angle to their surfaces.

7 A plywood panel adapted to be formed into compound bends, said panel comprising a plurality of layers of -wood veneer, the layers of veneers having the grain thereof running at right angle to 'the grain in the adjacent layers of veneers, said Veneers being bonded together With an adhesive, said panels having a plurality of saw cuts formed therein in parallel relationship and completely through the panel, said saw cuts being directed angular-ly across the panel with respect to the longitudinal direction thereof and terminating short of the longitudinal edges and said saw cuts being formed at Ean angle of less than 90 to the surfaces of the panel.

S. A panel as in claim 7 wherein the saw cuts are directed across the panel at an angle of approximately and at an angle of approximately 45 to the surfaces off the panel.

References Cited in the le of this patent 

